U.S. patent number 10,066,852 [Application Number 15/079,643] was granted by the patent office on 2018-09-04 for water heater.
This patent grant is currently assigned to NORITZ CORPORATION. The grantee listed for this patent is NORITZ CORPORATION. Invention is credited to Makoto Hirotsu, Kazuhiro Nishimura.
United States Patent |
10,066,852 |
Nishimura , et al. |
September 4, 2018 |
Water heater
Abstract
A water heater has a primary heat exchanger having a first heat
transfer tube, a secondary heat exchanger having a second heat
transfer tube connected with the first heat transfer tube and being
located higher than the first heat transfer tube, and an outflow
path connected to an outflow-side end portion of the first heat
transfer tube. The outflow path has an offset flow path portion
including a rising portion which rises upward or obliquely upward
from a connecting portion of the outflow path and the outflow-side
end portion of the first heat transfer tube or from the vicinity of
the connecting portion, the offset flow path portion being offset
at a position higher than the outflow-side end portion. When hot
water supply is temporally stopped, the water at high temperature
in the first heat transfer tube flows into the offset flow path
portion, thereby inhibiting such a disadvantage that water having a
lower temperature than a target temperature is supplied because of
a natural convection at the time of restarting hot water
supply.
Inventors: |
Nishimura; Kazuhiro (Kobe,
JP), Hirotsu; Makoto (Kobe, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NORITZ CORPORATION |
Hyogo |
N/A |
JP |
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|
Assignee: |
NORITZ CORPORATION (Hyogo,
JP)
|
Family
ID: |
57147547 |
Appl.
No.: |
15/079,643 |
Filed: |
March 24, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160313027 A1 |
Oct 27, 2016 |
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Foreign Application Priority Data
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Apr 21, 2015 [JP] |
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2015-086694 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24H
9/128 (20130101); F24H 9/2035 (20130101); F24H
9/144 (20130101); F24H 8/00 (20130101); F24H
9/146 (20130101); F24H 9/001 (20130101); F24H
1/46 (20130101); F24H 1/445 (20130101); F24H
1/165 (20130101); Y02B 30/00 (20130101) |
Current International
Class: |
F24H
1/16 (20060101); F24H 9/20 (20060101); F24H
1/46 (20060101); F24H 1/44 (20060101); F24H
9/14 (20060101); F24H 9/12 (20060101); F24H
8/00 (20060101); F24H 9/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2020794 |
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Nov 1979 |
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GB |
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2005-207687 |
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Aug 2005 |
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JP |
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2007-032935 |
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Feb 2007 |
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JP |
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2013-011409 |
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Jan 2013 |
|
JP |
|
Other References
Water Pump Controls,
http://inspectapedia.com/water/Water_Pump_Controls.php, Pictures
dated 2012. cited by examiner.
|
Primary Examiner: McAllister; Steven B
Assistant Examiner: Anderson, II; Steven
Attorney, Agent or Firm: Studebaker & Brackett PC
Claims
The invention claimed is:
1. A water heater comprising: a primary heat exchanger having a
first heat transfer tube configured to recover heat from heating
gas; a secondary heat exchanger having a second heat transfer tube
configured to further recover heat from heating gas of which heat
has been recovered in the primary heat exchanger, the secondary
heat transfer tube being connected with the first heat transfer
tube and being located higher than the first heat transfer tube; a
bypass flow path connecting an inflow path connected with an
inflow-side end portion of the second heat transfer tube and an
outflow path connected with an outflow-side end portion of the
first heat transfer tube; the outflow path having an offset flow
path portion including a rising portion which rises upward or
obliquely upward directly or indirectly from a connecting portion
of the outflow path with the outflow-side end portion of the first
heat transfer tube, the offset flow path portion being offset at a
position higher than the outflow-side end portion; a first trap
flow path provided in an area of the inflow path, wherein a lowest
portion of the first trap flow path is lower than the outflow-side
end portion of the first heat transfer tube; and a second trap flow
path provided for an intermediate flow path connecting the first
heat transfer tube and the second heat transfer tube, wherein the
inflow path extends downward from the secondary heat exchanger,
wherein the outflow path extends downward from the primary heat
exchanger except for the offset flow path portion, wherein the
offset flow path portion further comprises a horizontal portion
connected with an upper end portion of the rising portion and
extending in a horizontal direction, and wherein the offset flow
path portion does not extend downward.
2. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case into which heating gas is supplied and
in which the first heat transfer tube is housed, and wherein the
horizontal portion and the rising portion of the offset flow path
portion are in a non-contact condition with the case.
3. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case having a circumferential wall portion
into which heating gas is supplied, the circumferential wall
portion provided in a shape of a frame and an upper flange portion,
the upper flange portion being provided at an upper portion of the
circumferential wall portion and mounting the secondary heat
exchanger directly or indirectly, wherein the first heat transfer
tube is configured in such a manner that a plurality of straight
tube bodies supported by the circumferential wall portion are
connected via a plurality of connection tube bodies arranged
outside of the circumferential wall portion, wherein a space is
provided between the plurality of connection tube bodies and the
upper flange portion, and wherein the horizontal portion is
configured to extend into the space or face the space.
4. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case having a circumferential wall portion
into which heating gas is supplied, the circumferential wall
portion provided in a shape of a frame and an upper flange portion,
the upper flange portion being provided at an upper portion of the
circumferential wall portion and mounting the secondary heat
exchanger directly or indirectly, wherein the first heat transfer
tube is configured in such a manner that a plurality of straight
tube bodies supported by the circumferential wall portion are
connected via a plurality of connection tube bodies arranged
outside of the circumferential wall portion, and wherein the
horizontal portion is located under the upper flange portion and is
departed from an outer surface of the case in a horizontal
direction further than the plurality of connection tube bodies.
5. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case having a circumferential wall portion in
a shape of a frame into which heating gas is supplied, the
circumferential wall portion being constituted with a plurality of
side wall portions, and wherein the offset flow path portion is
configured to wind around at least two side wall portions in a
non-contact condition.
6. The water heater according to claim 5, wherein an end portion of
the offset flow path portion and the inflow-side end portion have a
pair of pipe connection ports, and wherein the offset flow path
portion is configured in such a manner that the pair of pipe
connection ports are provided on the same side of the case in a
longitudinal width direction or in a lateral width direction.
7. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case having a circumferential wall portion in
a shape of a frame into which heating gas is supplied, the
circumferential wall portion being constituted with a plurality of
side wall portions, and wherein an end portion of the offset flow
path portion and the inflow-side end portion have a pair of pipe
connection ports, and the pair of pipe connection ports are
provided on the same side of the case in a longitudinal width
direction or in a lateral width direction.
8. The water heater according to claim 1, wherein the first heat
transfer tube is configured in such a manner that a plurality of
straight tube bodies are arranged with a space in a direction
intersecting with an axially longitudinal direction and are
consecutively connected in a meandering manner via a plurality of
connection tube bodies, and wherein the primary heat exchanger
comprises a case into which heating gas is supplied and the heat
transfer tube in a meandering manner is provided in a single stage
in a vertical height direction in the case.
9. The water heater according to claim 1, wherein the primary heat
exchanger comprises a case into which heating gas is supplied and
in which the first heat transfer tube is housed, and a third heat
transfer tube arranged in side-by-side to the first heat transfer
tube in the case, and wherein the secondary heat exchanger
comprises an additional case into which heating gas of which heat
has been recovered in the first heat transfer tube and the third
heat transfer tube is supplied and in which the second heat
transfer tube is housed, and comprises a fourth heat transfer tube
arranged in side-by-side to the second heat transfer tube in the
additional case.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a water heater such as a gas water
heater.
Description of the Related Art
Specific example of a water heater is a latent heat recovery type
shown in FIG. 11A. In a water heater WH shown in FIG. 11A, water is
heated by recovering sensible heat and latent heat from combustion
gas generated by a burner 5 using a primary heat exchanger HE1 and
a secondary heat exchanger HE2. Water supplied to an inflow port
for water 20 passes through an inflow path for water 2, flows to be
heated in a second heat transfer tube T2 of the secondary heat
exchanger HE2, then passes through an intermediate flow path 3,
flows to be heated in a first heat transfer tube T1 of the primary
heat exchanger HE1, and passes through an outflow path for hot
water 4, thereby reaching an outflow port for hot water 40. The
outflow path 4 and the inflow path 2 are connected via a bypass
flow path 21 and the temperature of outflowing water is
controllable at a target value by controlling the amount of water
to be flown into the outflow path 4 through the bypass flow path 21
from the inflow path 2.
In the water heater WH, when hot water supply is restarted sometime
after being stopped, there is a disadvantage such that the
temperature of water (the temperature of the water flown from the
outflow port 40) temporally becomes lower than a target
temperature. Such a disadvantage is caused when a natural
convection of water shown with the arrows N1 to N5 in FIG. 11B is
generated at the time of stopping hot water supply. Such a natural
convection is caused by the following principle. When hot water
supply is stopped, the water in the first heat transfer tube T1
passes through the intermediate flow path 3 and goes up toward the
second heat transfer tube T2 because the water in the first heat
transfer tube T1 has a higher temperature and a smaller specific
gravity than the water in the second heat transfer tube T2. Then,
the water in the second heat transfer tube T2 flows toward the
inflow path 2. When water flows into the inflow path 2, the water
which is not heated and has a low temperature in the bypass flow
path 21 flows into the outflow path 4. When hot water supply is
restarted under such a condition, water which is not heated and at
a low temperature and which has flown into the outflow path 4 from
the bypass flow path 21 reaches the outflow port 40 and is supplied
to a predetermined destination. As a result, there is a worry that
the water having a relatively lower temperature than a target
temperature is supplied to the destination.
It is desirable that such a disadvantage is appropriately
prevented. In the conventional art, a trap flow path 99 is provided
for the intermediate flow path 3 connecting the first and the
second heat transfer tubes T1, T2 as shown in FIG. 11C (referring
to Patent Literatures 1 and 2). In such a case, the trap flow path
99 inhibits the water in the first heat transfer tube T1 from going
up toward the second heat transfer tube T2 at the time of stopping
hot water supply. Therefore, "natural convection of water" as
mentioned above is inhibited.
There is a case that the water in the first heat transfer tube T1
is not adequately prevented from going up toward the second heat
transfer tube T2 only by providing the trap flow path 99 for the
intermediate flow path 3. The applicant of the present invention
has already proposed a first heat transfer tube provided in a
single stage in the vertically height direction and in a meandering
manner in plan view as disclosed in Patent Literature 3. However,
in such a case, it is further difficult to prevent the
above-mentioned natural convection. It is because that the
temperature of the water in an upper tube is lower than that in a
lower tube when the first heat transfer tube T1 is constituted with
two tube bodies up and down as shown in FIG. 11A to FIG. 11C, so
that the natural convection shown in FIG. 11B is slightly weakened;
on the other hand, such a situation does not occur when the first
heat transfer tube T1, meandering in plan view, is provided
vertically in a single stage as mentioned above.
CITATION LIST
Patent Literature 1: Japanese Unexamined Patent Publication No.
2005-207687
Patent Literature 2: Japanese Unexamined Patent Publication No.
2007-32935
Patent Literature 3: Japanese Unexamined Patent Publication No.
2013-11409
SUMMARY OF THE INVENTION
An object of the present invention is to provide a water heater
capable of appropriately inhibiting or preventing the
above-mentioned disadvantages.
The present invention proposes the following technical measures for
solving the above-mentioned problems.
A water heater provided in one aspect of the present invention has
a primary heat exchanger having a first heat transfer tube
configured to recover heat from heating gas, and a secondary heat
exchanger having a second heat transfer tube configured to further
recover heat from heating gas of which heat has been recovered in
the primary heat exchanger, the secondary heat transfer tube being
connected with the first heat transfer tube and being located
higher than the first heat transfer tube. The water heater further
has a bypass flow path connecting an inflow path connected with an
inflow-side end portion of the second heat transfer tube with an
outflow path connected with an outflow-side end portion of the
first heat transfer tube. The outflow path has an offset flow path
portion including a rising portion which rises upward or obliquely
upward from a connecting portion of the outflow path and the
outflow-side end portion of the first heat transfer tube or from
the vicinity of the connecting portion, and the offset flow path
portion is offset at a position higher than the outflow-side end
portion.
Preferably, the offset flow path portion further has a horizontal
portion connected with an upper end portion of the rising portion
and extending substantially in a horizontal direction.
Preferably, the primary heat exchanger has a case into which
heating gas is supplied and in which the first heat transfer tube
is housed, and the horizontal portion and the rising portion of the
offset flow path portion are in a non-contact condition with the
case.
Preferably, the primary heat exchanger has a case having a
circumferential wall portion in a shape of a frame and an upper
flange portion, heating gas being supplied into the circumferential
wall portion, the upper flange portion being provided at an upper
portion of the circumferential wall portion and mounting the
secondary heat exchanger directly or indirectly. The first heat
transfer tube is configured in such a manner that a plurality of
straight tube bodies supported by the circumferential wall portion
are connected via a plurality of connection tube bodies arranged
outside of the circumferential wall portion.
Preferably, a space is provided between the plurality of connection
tube bodies and the upper flange portion, and the horizontal
portion is configured to extend into the space or face the
space.
Preferably, the horizontal portion is located under the upper
flange portion and is departed from an outer surface of the case in
a horizontal direction further than the plurality of connection
tube bodies.
Preferably, the primary heat exchanger has a case having a
circumferential wall portion in a shape of a frame into which
heating gas is supplied, the circumferential wall portion being
constituted with a plurality of side wall portions, and the offset
flow path portion is configured to wind around at least two side
wall portions in a non-contact condition.
Preferably, an end portion of the offset flow path portion and the
inflow-side end portion have a pair of pipe connection ports, and
the offset flow path portion is configured in such a manner that
the pair of pipe connection ports are arranged on the same side of
the case in a longitudinal width direction or in a lateral width
direction.
Preferably, the water heater in one aspect of the present invention
further has a first trap flow path provided in an area, close to
the second heat transfer tube, of the inflow path.
Preferably, a lowest portion of the first trap flow path is lower
than the outflow-side end portion of the first heat transfer
tube.
Preferably, the water heater in the one aspect of the present
invention further has a second trap flow path provided for an
intermediate flow path connecting the first heat transfer tube and
the second heat transfer tube.
Preferably, the first heat transfer tube is configured in such a
manner that a plurality of straight tube bodies are arranged with a
space in a direction intersecting with an axially longitudinal
direction and are consecutively connected in a meandering manner
via a plurality of connection tube bodies. The primary heat
exchanger has a case into which heating gas is supplied and the
heat transfer tube in a meandering manner is provided in a single
stage in a vertical height direction in the case.
Preferably, the primary heat exchanger has a case into which
heating gas is supplied and in which the first heat transfer tube
is housed, and a third heat transfer tube arranged in side-by-side
to the first heat transfer tube in the case. The secondary heat
exchanger has an additional case into which heating gas of which
heat has been recovered in the first heat transfer tube and the
third heat transfer tube is supplied and in which the second heat
transfer tube is housed, and has a fourth heat transfer tube
arranged in side-by-side to the second heat transfer tube in the
additional case.
Other characteristics and advantages of the present invention will
be apparent in the following detailed description of the preferred
embodiments referring to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic front sectional view showing one
embodiment of a water heater of the present invention.
FIG. 2 is a sectional view along the line II to II in FIG. 1.
FIG. 3 is a sectional view along the line III to III in FIG. 1.
FIG. 4 shows a plane section of a primary heat exchanger of the
water heater shown in FIG. 1.
FIG. 5 is a front view of the primary heat exchanger shown in FIG.
4.
FIG. 6 is a diagrammatic front sectional view showing another
embodiment of the water heater of the present invention.
FIG. 7 is a sectional view along the line VII to VII in FIG. 6.
FIG. 8 is a diagrammatic front sectional view showing a major part
of another embodiment of the water heater of the present
invention.
FIG. 9 shows a plane section of another embodiment of the present
invention.
FIG. 10A is a front view of the embodiment in FIG. 9 and FIG. 10B
shows its left side view.
FIG. 11A to FIG. 11C diagrammatically illustrate an embodiment of
the conventional art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Preferred embodiments of the present invention are explained below
with reference to the accompanying drawings.
In the explanation to be mentioned below, the elements same as or
similar to those in the conventional art shown in FIG. 11A to FIG.
11C are allotted with the same reference numerals for easy
understanding.
FIG. 1 to FIG. 5 show one embodiment of a water heater to which the
present invention is applied.
In FIG. 1, a water heater WH1 in the embodiment of the present
invention has a similar basic structure to that disclosed in Patent
Literature 3 and has a burner 5, the primary heat exchanger HE1,
the secondary heat exchanger HE2, and an exterior case 9
surrounding them.
The water heater WH1 is capable of separately supplying hot water
in two lines, namely a hot water supply system, and a hot water
heating system (or a reheating system for bath). The primary heat
exchanger HE1 and the secondary heat exchanger HE2 have two water
paths in one case, respectively. In the primary heat exchanger HE1,
a first and a third heat transfer tubes T1, T3 to be mentioned
later are housed in a case 6. In the secondary heat exchanger HE2,
a second and a fourth heat transfer tubes T2, T4 to be mentioned
later are housed in a case 7.
The bottom portion or the side portion of the exterior case 9 is
provided with inflow ports for water 20, 90a to which external
inflow tubes of water 8a, 8c are connected and with outflow ports
for hot water 40, 91a to which external outflow tubes of water 8b,
8d are connected. On a hot water supply side, the water supplied to
the inflow port for water 20 is supplied to a header 75b of the
secondary heat exchanger HE2 through the inflow path for water 2,
thereby circulating in the second heat transfer tube T2. Then, the
water is supplied to the primary heat exchanger HE1 through a
header 75a of the secondary heat exchanger HE2 and the intermediate
flow path 3, thereby circulating in the first heat transfer tube
T1. After passing through the first heat transfer tube T1, the
water reaches the outflow port for hot water 40 through the outflow
path for hot water 4. The inflow path 2 and the outflow path 4 are
connected via the bypass flow path 21 and a mixing valve V1. The
mixing valve V1 is capable of mixing the non-heated water flown
into the bypass flow path 21 from the inflow path 2 and the water
in the outflow path 4 at a desirable rate. By mixing the waters,
the temperature of the water reaching the outflow port 40 is able
to be controlled at a target water temperature. The water reaching
the outflow port 40 is supplied to a kitchen and a lavatory.
In this embodiment, for stabilizing water temperature at the time
of restarting hot water supply, an offset flow path portion 41 is
provided for the outflow path 4, and a first trap flow path 22 and
a second trap flow path 32 are provided for the inflow path 2 and
the intermediate flow path 3. The details are explained later.
On a hot water heating side (or on a bath reheating side), the
water supplied to the inflow port 90a is supplied to a header 75d
of the secondary heat exchanger HE2 through the inflow path for
water 90, flows in the fourth heat transfer tube T4, and then is
sent to the third heat transfer tube T3 of the primary heat
exchanger HE1 through a header 75c and the intermediate flow path
92. Thereafter, the water reaches the outflow port 91a through the
outflow path for hot water 91. The outflow path 91 and the inflow
path 90 are connected via a bypass flow path 93 and a mixing valve
V2 like the hot water supply side. The water reaching the outflow
port 91a is sent to a heating terminal device (or a bathtub), not
shown. In case of hot water heating (or a bath reheating), water
temperature is allowed to be unstable and to be slightly changed at
the beginning of hot water supply, unlike a hot water supply
system. Therefore, the hot water heating side (on the side of the
third and the fourth heat transfer tubes T3, T4) is not provided
with means corresponding to the offset flow path portion 41, the
first and the second trap flow paths 22, 32, which are provided for
the hot water supply side (on the side of the first and the second
heat transfer tubes T1, T2). However, such means can be provided
for the hot water heating side, different from the embodiment of
the present invention.
The burner 5, for example a gas burner, burns fuel gas utilizing
combustion air sent upwardly from a fan 51 into a burner case 50.
The burner 5 has a first combustion area A1 and a second combustion
area A2 in which combustion drive control is separately executed.
The upper area is separated by a partition member 52 and combustion
gas generated in the first and the second combustion areas A1, A2
proceeds separately toward the first and the third heat transfer
tubes T1, T3.
The primary heat exchanger HE1 recovers sensible heat from the
combustion gas and is housed in the case 6 mounted on the burner
case 50 in such a manner that the first and the third heat transfer
tubes T1, T3 are arranged in side-by-side with a partition member
68 interposed therebetween. The case 6 has a circumferential wall
portion 66 in the shape of a rectangular frame of which upper face
and lower face are opened, and has an upper flange portion 67
provided at an upper portion of the circumferential wall portion
66. The upper flange portion 67 is provided so as to be assembled
with the secondary heat exchanger HE2. The combustion gas is
supplied to the circumferential wall portion 66 from downward.
The first and the third heat transfer tubes T1, T3 are finned tubes
made of copper and provided with a plurality of fins 10, 13. As
shown in FIG. 4 and FIG. 5, the first heat transfer tube T1 is in a
meandering manner in plan view such that a plurality of straight
tube bodies 11 arranged in the lateral width direction of the case
6 are consequently connected via connection tube bodies 12
substantially in the shape of a letter U and are arranged in a
single stage in the vertical height direction. The third heat
transfer tube T3 is configured, like the first heat transfer tube
T1, in such a manner that a plurality of straight tube bodies 14
are consequently connected via connection tube bodies 15; however
the straight tube bodies 14 are arranged in, for example, two
stages in the vertical height direction.
In FIG. 1, the secondary heat exchanger HE2 recovers latent heat
from the combustion gas passing through the primary heat exchanger
HE1. In the case 7 mounted on the primary heat exchanger HE1, a
plurality of second and the fourth heat transfer tubes T2, T4 are
arranged in side-by-side with a partition board 74 interposed
therebetween. The second and the fourth heat transfer tubes T2, T4
are, for example, helical tube bodies with different sizes and are
overlapped in a substantially concentric manner, like the heat
transfer tube of the secondary heat exchanger in Patent Literature
3. As shown in FIG. 2, the combustion gas upwardly passing through
the position where the first heat transfer tube T1 is provided
flows into the case 7 through an air supply port 71a of a bottom
wall portion 70a of the case 7, works on the second heat transfer
tubes T2, and reaches a discharge port 72 of a front wall portion
70b. As shown in FIG. 3, the combustion gas upwardly passing
through the position where the third heat transfer tube T3 is
provided flows into the case 7 through an air supply port 71b of
the bottom wall portion 70a of the case 7, works on the fourth heat
transfer tubes T4, and reaches the discharge port 72.
In FIG. 1 and FIG. 4, one end portion of a straight tube body 11',
located close to an end of the case 6 in the width direction, of
the first heat transfer tube T1 is an inflow-side end portion 11a.
The inflow-side end portion 11a is connected with an auxiliary tube
16, substantially in the shape of a letter U, having a tube
connection port 16a in order to facilitate pipe connection with the
header 75a of the secondary heat exchanger HE2. A series of water
flow path from the header 75a to the inflow-side end portion 11a is
the above-mentioned intermediate flow path 3. One end portion of a
straight tube body 11'', close to the center of the case 6, of the
first heat transfer tube T1 is an outflow-side end portion 11b. The
outflow-side end portion 11b is connected with an auxiliary tube 42
having a pipe connection port 42a (omitted in FIG. 1). A series of
water flow path from the outflow-side end portion 11b to the
outflow port 40 is the above-mentioned outflow path 4.
As shown in FIG. 1 and FIG. 5, the offset flow path portion 41 is a
part of the outflow path 4 and is constituted using the auxiliary
tube 42. Specifically, the offset flow path portion 41 has a rising
portion 41a rising obliquely upward (or upward) from a connecting
portion J of the outflow-side end portion 11b and the auxiliary
tube 42 or from the vicinity of the connecting portion J, and has a
horizontal portion 41b connected to the upper end portion of the
rising portion 41a so as to extend substantially in the horizontal
direction. The offset flow path portion 41 is offset at a higher
position than the outflow-side end portion 11b, and is preferably
in a non-contact condition with the case 6.
The first heat transfer tube T1 is at substantially the same height
as the lower straight tube body 14 of the third heat transfer tube
T3. A space S1 is formed between the connection tube bodies 12 of
the first heat transfer tube T1 and the upper flange portion 67 of
the case 6 as shown in FIG. 2, the vertical width La of the space
S1 being larger than the outer diameter of the offset flow path
portion 41. The horizontal portion 41b of the offset flow path
portion 41 is provided above the connection tube bodies 12 so as to
extend into or face the space S1. Since the offset flow path
portion 41 is thus provided in the space S1, originally having no
use, the offset flow path portion 41 is provided without enlarging
the primary heat exchanger HE1.
In FIG. 1, the first trap flow path 22 is provided for part of the
inflow path 2 in the vicinity of the header 75b of the secondary
heat exchanger HE2. The first trap flow path 22, like a commonly
used U-shaped trap, has a pair of falling flow paths 22a extending
downward from both sides of the flow path 22 and the lower portions
of the falling low paths 22a are connected. Preferably, height Hb
of the lowest portion of the first trap flow path 22 is smaller
than height Ha of the outflow-side end portion 11b.
The intermediate flow path 3 is provided with the second trap flow
path 32. The second trap flow path 32, shaped similar to the first
trap flow path 22, has a pair of falling flow paths 32a extending
downward from both sides of the flow path 32 and the lower portions
of the falling flow paths 32a are connected. Preferably, height Hc
of the lowest portion of the second trap flow path 32 is smaller
than height Ha of the outflow-side end portion 11b. The second trap
flow path 32 is provided for part of the intermediate flow path 3
closer to the outflow-side end portion 11b.
Next, operational effect of the above-mentioned water heater WH1 is
explained.
As mentioned above, when hot water supply is executed such that:
the water flown into the inflow path 2 from the inflow port 20
flows into the second heat transfer tube T2, the intermediate flow
path 3, the first heat transfer tube T1 and the outflow path 4;
combustion gas generated in the first combustion area A1 in the
burner 5 works on the first and the second heat transfer tubes T1,
T2 in order. When such hot water supply is temporally stopped, the
water temperature in the first heat transfer tube T1 becomes higher
than that in the second heat transfer tube T2 and the specific
gravity of the water in the first heat transfer tube T1 becomes
smaller than that in the second heat transfer tube T2. Then, the
water in the first heat transfer tube T1 positively flows into the
offset flow path portion 41 from the outflow-side end portion 11b.
The temperature distribution of the water in the first heat
transfer tube T1 on the outflow side is higher than that on the
inflow side, so that the amount of the water flowing from the
outflow-side end portion 11b to the offset flow path portion 41
increases. The offset flow path portion 41 is constituted such that
the horizontal portion 41b is connected with the rising portion
41a, thereby enlarging the volume of the offset flow path portion
41 and enabling smooth flow of a large amount of water, going up in
the rising portion 41a, into the horizontal portion 41b. As a
result, a large amount of water is able to positively flow from the
outflow-side end portion 11b to the offset flow path portion
41.
When the water in the first heat transfer tube T1 flows into the
offset flow path portion 41 as mentioned above, the amount of the
water flown from the first heat transfer tube T1 to the second heat
transfer tube T2 via the intermediate flow path 3 reduces by the
amount of water flowing from the first heat transfer tube T1 to the
offset flow path portion 41. As a result, the natural convection of
water as shown in FIG. 11B is inhibited and water, which is not
heated and is at low temperature, in the bypass flow path 21 is
inhibited from flowing into the outflow path 4. Such a phenomenon
of outflow of water at relatively lower temperature than a target
water temperature from the outflow port 40 is suitably inhibited
and effect of stabilizing the water temperature is obtained.
Since the inflow path 2 has the first trap flow path 22, when the
water in the first heat transfer tube T1 tries to flow into the
second heat transfer tube T2 through the intermediate flow path 3
at the time of stopping hot water supply as mentioned above, such a
flow is inhibited by the first trap flow path 22. In addition, the
second trap flow path 32 provided for the intermediate flow path 3
exerts similar operational effect of inhibiting the above-mentioned
water flow. Therefore, the natural convection shown in FIG. 11B is
thoroughly prevented and hot water supply temperature at the time
of restarting hot water supply is more stabled.
The offset flow path portion 41, in a non-contact condition with
the case 6, is not excessively heated by the conductive heat
generated from the case 6. When the offset flow path portion 41 is
excessively heated, scale is likely to be generated therein;
however, such a worry is able to be solved in the present
embodiment.
FIG. 6 to FIG. 10A and FIG. 10B show another embodiment of the
present invention. In these figures, the elements same as or
similar to those in the precedent embodiment are allotted with the
same reference numerals and the redundant explanation is
omitted.
In a water heater WH2 shown in FIG. 6, a plurality of straight tube
bodies 14 of the third heat transfer tube T3 are provided in a
single stage in the vertical height direction, thereby reducing the
entire vertical height of the case 6 of the primary heat exchanger
HE1. The horizontal portion 41b of the offset flow path portion 41
is provided below the upper flange portion 67 of the case 6 and at
a position departing from the outer face of the case 6 in the
horizontal direction further than the connection tube bodies 12,
namely at a position closer to the left in the figure, as shown in
FIG. 7. The horizontal portion 41b is of course higher than the
outflow-side end portion 11b of the first heat transfer tube T1. In
this embodiment, the horizontal portion 41b and the outflow-side
end portion 11b are partially overlapped in the vertical height
direction. Such a positional relation is acceptable in the present
invention. It is enough that the center of at least a part of the
offset flow path portion 41 is higher than the center of the
outflow-side end portion 11b.
In a water heater WH3 shown in FIG. 8, the horizontal portion 41b
of the offset flow path portion 41 is connected with the bypass
flow path 21 for inflow of the water from the inflow path 2 and the
mixing valve V1 is further provided.
In this embodiment, when the water in the first heat transfer tube
T1 positively flows into the offset flow path portion 41 at the
time of stopping hot water supply, there is such effect that the
non-heated water in the inflow path 2 has difficulty to flow into
the offset flow path portion 41 through the bypass flow path 21.
Therefore, the natural convection of water as shown in FIG. 11B is
more thoroughly prevented.
A primary heat exchanger HE1' shown in FIG. 9, FIG. 10A and FIG.
10B is different from the heat exchanger HE1 in the above-mentioned
embodiment in that the third heat transfer tube T3 is not provided
and only the first heat transfer tube T1 is provided for hot water
supply as the heat transfer tube. Therefore, the water heater
constituted with the primary heat exchanger HE1' is used for hot
water supply, and a burner and a secondary heat exchanger are
provided corresponding to the primary heat exchanger HE1'. The
circumferential wall portion 66 of a case 6A is constituted with
first to fourth side wall portions 66a-66d.
The offset flow path portion 41 of the primary heat exchanger HE1'
has a bent portion 41c curved or crooked seen in plan view. The
bent portion 41c constitutes the rising portion 41a. Thus, the
offset flow path portion 41 is located beside a part of the first
side wall portion 66a of the case 6A and the second side wall
portion 66b and winds around them in a non-contact condition. The
pipe connection port 42a at the terminal end of the offset flow
path portion 41 and the pipe connection port 16a of the inflow-side
end portion 11a are provided on the same face of the case 6A in the
longitudinal width direction or in the lateral width direction of
the case 6A.
In this embodiment, the entire length of the offset flow path
portion 41 is preferably increased and the volume thereof is also
increased. Therefore, such an embodiment is suitable for positively
flowing a lot of water in the offset flow path portion 41. The
offset flow path portion 41 is in a non-contact condition with the
first and the second side wall portions 66a, 66b of the case 6A, so
that the offset flow path portion 41 is not excessively heated by
the conductive heat generated from the case 6A. As mentioned above,
when the offset flow path portion 41 is excessively heated, scale
is easily generated therein. However, such a worry is solved in
this embodiment. The offset flow path portion 41 is moderately
close to the case 6A, thereby effectively heating water using the
heat generated from the case 6A. A pair of pipe connection ports
42a, 16a are provided on the same side of the case 6A, thereby
facilitating connection of the pipe members constituting the
outflow path 4 and the intermediate flow path 3.
The present invention is not limited to the above-mentioned
embodiments. The specific configuration of the members of the water
heater of the present invention is freely designed within the
intended scope of the present invention.
The offset flow path portion in the present invention is preferably
constituted in such a manner that the outflow path is provided with
the rising portion rising upward or obliquely upward from the
connecting portion of the outflow path and the outflow-side end
portion of the first heat transfer tube or from the vicinity of the
connecting portion, and that a part of the outflow path is offset
at a position higher than the above-mentioned outflow-side end
portion. The connecting portion of the outflow path and the
outflow-side end portion of the first heat transfer tube is a
connecting portion in which the piping members constituting the
outflow path and the outflow-side end portion of the first heat
transfer tube are physically connected by means of welding or
brazing. However, the connecting portion is not limited. For
example, when a tube constituting the first heat transfer tube
extends long from the inside of the case to the outside thereof and
the extending portion actually fulfills a role of the outflow path,
the boundary area of part of the tube being actually the outflow
path and part of the tube being actually the heat transfer tube is
the connecting portion of the outflow path and the outflow-side end
portion of the first heat transfer tube in the present invention.
The offset flow path portion is not limited to have the horizontal
portion. The offset flow path portion can be provided with a slowly
upward slant portion, or with a downward slant portion after the
horizontal portion or the slant portion.
The primary heat exchanger is not limited such that a plurality of
straight tube bodies are provided in a single stage in the vertical
height direction and the primary heat exchanger can be constituted
in such a manner that a plurality of straight tube bodies are
provided in several stages. The secondary heat exchanger is only
required to recover heat from heating gas which has passed through
the primary heat exchanger. In place of a helical heat transfer
tube, a heat transfer tube in a meandering manner, in a straight
manner or in another manner can be used. Heating gas can be
generated by an oil burner instead of a gas burner, or can be
exhaust gas at high temperature discharged from a power generation
part of a cogeneration system.
* * * * *
References